Effects of different biofloc sizes on the short‐term stress of Japanese seabass, Lateolabrax japonicus (Cuvier), juveniles reared in biofloc aquaculture systems

A 5-day short-term stress response experiment was conducted to investigate the effects of different biofloc sizes on a culture of Japanese seabass, Lateolabrax japonicus (Cuvier), juveniles. The fish were divided into four groups: small particle size (SG), medium particle size (MG), large particle size (LG) and clear water control (CG) groups. The diameters of the median particle size and coarse telomere of the SG, MG and LG were 45.61 μm, 185.75 μm and 272.43 μm and 211.04 μm, 399.55 μm and 859.45 μm respectively. The cortisol content in the SG group increased during the experiment and was significantly different from those of the other three groups (p < 0.05); additionally, the total protein, blood glucose, triglyceride and total cholesterol levels were significantly different at different times during the study (p < 0.05). In most cases, the alkaline phosphatase activity of the SG group showed a downward trend, which is contrary to the superoxide dismutase and catalase activities observed in the SG and MG. The gill lamellae of the SG, MG and LG were damaged to a certain extent. Overall, the results showed that bioflocs with small particle size exerted the most negative effect on Japanese seabass juveniles as short-term stressors.